Biochar Reactivity Research Articles

Catalytic CO2 Gasification of Rice Husk Char for Syngas and Silica-Based Nickel Nanoparticles Production

The nickel-catalyzed CO2 gasification of rice husk char (RHC) was studied. In this work, carbon conversion is studied by thermogravimetric analysis (TGA) and a packed-bed reactor. The key influence parameters including nickel-loading amount and gasification temperature were investigated. In the absence of nickel, the carbon conversion efficiency of 100% was achieved in 40 min at 1000 °C, whereas this time was extended to 130 min at 700 °C. Although the use of high temperatures improved char reactivity, relatively high temperatures can shift the reaction rate toward the pore-diffusion-controlled regime. Also, the addition of nickel catalyst can improve the biochar reactivity by reducing the activation energy, in terms of the improvement of the carbon conversion and its rate. In the view of RHA Ni recycling, the silica-based nickel nanoparticles could be recycled in various catalytic applications.

Effect of Biochar as Reductant on Magnetizing-roasting Behavior of Pyrite Cinder

The effect of biochar substituted for anthracite as reductant on magnetizing-roasting pyrite cinder was investigated. The key of magnetizing-roasting is the gasification reaction between reductants and CO2. Since biochar could react with CO2 more rapidly at lower temperature, the reactivity of biochar is better than that of anthracite. The gasification of biochar could produce reducing condition of φCO / (φCO + φCO2) about 10% – 20% between 700–800 °C, which is in accord with the atmosphere and temperature of Fe2O3 reduction. So it is beneficial to the reduction of iron mineral of pyrite cinder. Compared with anthracite, biochar could decrease the roasting temperature from 825 to 750 °C and roasting time from 20 to 15 min, which shows that a better effect of magnetization could be obtained in the condition of lower temperature and shorter time. Using biochar as reductant, iron concentrate extracted from pyrite cinder as about 61% iron grade could be produced, and the recovery is over 90% under the condition of above 90% grinding particle less than 0.045 mm and magnetic intensity of 0.121–0.194 T.

Assessment of the surface chemistry of wood-derived biochars using wet chemistry, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy

In order to understand the reactivity of biochar in soil, we thoroughly examined the carbonaceous surface of different biochars, paying particular attention to the distribution of oxygen-containing functional groups. Biochar was produced from pine, poplar and willow at two different temperatures (400 and 550°C) and characterised using elemental analysis and wet chemistry (Boehm and potentiometric titrations, cation-exchange capacity (CEC) measurement). In addition, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses were performed on both untreated and acid-washed biochar samples. Qualitative relationships were observed between data generated from the titration methods under investigation and XPS analyses, both describing the general distribution of oxygen-containing surface functional groups. Total acidity of biochar ranged widely, between 32 and 1067 mmol kg–1, and was mostly attributed to the presence of hydroxyl or phenol groups. The number of functional groups containing oxygen decreased with increasing pyrolysis temperature, mainly because of a decrease in the content of phenol groups. A quantitative comparison of titrations and CEC (i.e. biochar’s ion-exchange capacity) measurements was compromised by a masking effect caused by the biochar’s inorganic fraction (<8%). An acid-washing step with nitric acid was shown not to alter the biochar surface systematically. The use of potentiometric titrations with an acid-washing pretreatment proved to be suitable to quantify biochar acidic functional groups, and hence biochar acidity.

Rates and Mechanisms of Zn2+ Adsorption on a Meat and Bonemeal Biochar

Biochars produced from meat and bonemeal (MBM) waste materials contain large amounts of calcium phosphate and are potentially useful sorbents for the remediation of metals. Because the reactivity of biochars depends strongly upon the conditions used in their production, the objective of this study was to evaluate the rates and mechanisms of Zn sorption onto a commercially supplied MBM biochar prior to its application in a field-scale revegetation project. Sorption experiments varying pH, time, and Zn concentration found that, above pH 6.1, Zn adsorbed to MBM biochar quickly (within 5 h) with a maximum adsorption capacity of 0.65 mmol Zn g(-1). Synchrotron-based Zn K-edge extended X-ray absorption fine structure spectroscopy was consistent with a tetrahedral Zn bound to phosphate groups in a monodentate inner-sphere surface complex for all conditions tested. With an acidification pretreatment and at more acidic pH, MBM biochar causes precipitation of a ZnPO4 phase. On the basis of these results, this MBM biochar has a high capacity to rapidly adsorb Zn in adsorption experiments and can be considered a promising sorbent for Zn remediation of contaminated soils.

Can biochar and hydrochar stability be assessed with chemical methods?

Field application of biochar is intended to increase soil carbon (C) storage. The assessment of C storage potential of biochars lacks methods and standard materials. The reactivity of biochars and hydrochars may be one possible means of evaluating their environmental stability. The aim of this study was to evaluate the reactivity of biochar produced by gasification (GS) and hydrochar produced by hydrothermal carbonisation (HTC). The approach included analysis of the two different char types produced from the same three feedstocks. Moreover, we analysed the reactivity of Holocene charcoal (150 and 2000yr old) to evaluate whether or not their use as standard materials to represent stable biochar is meaningful. We assessed carbon loss following oxidation with acid dichromate as well as hydrolysis with HCl. Our results showed that chemical reactivity is not a straightforward approach for characterising the stability of biochar and hydrochar. Acid hydrolysis showed little difference between HTCs and GSs, despite the contrasting elemental composition. Using acid dichromate oxidation, we determined that GSs contained ca. 70% of oxidation resistant C while the proportion for HTCs was<10%. The different feedstocks had a slight, but significant, influence on the reactivity of GSs and HTCs. The content of oxidation resistant C decreased in the order 100yr old charcoal=GSs>2000yr old charcoal>HTCs>feedstock and was related to elemental composition. This shows that acid dichromate oxidation may allow differentiation of the reactivity of modern biochars but that there is not necessarily a relationship between reactivity and age of Holocene charcoals. As the chemical reactivity of biochars may change with exposure time in soil, it is poorly suited for assessing their environmental residence time.

Biochar as a Fuel: 3. Mechanistic Understanding on Biochar Thermal Annealing at Mild Temperatures and Its Effect on Biochar Reactivity

This study reports a mechanistic investigation on the thermal annealing process at mild temperatures (750 and 900 °C) and its effect on the reactivity of biochar prepared from the pyrolysis of a We...

Effect of Alkali and Alkaline Earth Metallic Species on Biochar Reactivity and Syngas Compositions during Steam Gasification†

Biochars were prepared from the pyrolysis of the wood, leaf, and bark components of mallee biomass in a fixed-bed reactor at 750 °C. The results show that the volatilization of inherent alkali and alkaline earth metallic (AAEM) species is 10−20% during the pyrolysis of raw wood, bark, and leaf samples. Acid treatment of the biochar samples was also carried out to prepare a set of acid-treated biochar samples. Although the majority of the inherent AAEM species were removed by acid-treatment, there are always some AAEM species that could not be removed for all biochars. Steam gasification experiments of both the raw and acid-treated biochar samples were carried out in a fixed-bed reactor at 750 °C and a steam concentration of 8.2 vol %. Data on the instantaneous syngas composition were obtained as a function of biochar conversion during steam gasification. Our data illustrated the importance of, in the study of steam gasification reaction mechanisms and kinetics of solid fuels such as biochars, optimizing t...